The present invention relates to rock reinforcing apparatus and, more specifically, to novel combined mechanical-resin rock bolt anchoring systems such as typically used in the support of mine roofs, and the like.
Among the more common means presently in use for reinforcing rock formations during mining, tunneling and excavating are elongated bolts or bars which are securely anchored in blind drill holes in the formation by mechanical expansion anchors, hardenable resin mixes which surround the end of the bolt within the hole, or both. Prior art systems employing a combination of mechanical and resin anchor means are discussed in U.S. Pat. No. 4,162,133, assigned to applicants' assignee, which discloses bolt anchoring apparatus and methods which involve common rotation of the bolt and an expansion anchor carried on the threaded end thereof to break a two-compartment resin package and mix the contents thereof. Cooperating structure associated with the bolt and/or anchor cause the two to be rotated together (i.e., relative rotation is prevented) when the bolt is turned in a counter-clockwise direction, tending to withdraw it from threaded engagement with the tapered nut of the expansion anchor. The cooperating structure, however, allows relative rotation in the opposite direction, whereby the anchor may be held stationary as the bolt is rotated in the opposite direction to draw the tapered nut into the hollow shell and effect expansion thereof. Thus, the bolt is anchored and tensioned prior to hardening of the resin mixture, which subsequently strengthens the bond between the bolt and rock formation.
Aforementioned U.S. Pat. No. 4,162,133 discloses a number of embodiments of means for rotationally locking the bolt and anchor in one direction of bolt rotation while permitting the anchor to be held stationary when the bolt is rotated in the opposite direction. An additional embodiment of such means is disclosed in copending application Ser. No. 945,225 of Gordon C. Evans, also assigned to applicants' assignee. The present invention is directed to, and has for a principal object the provision of, further novel embodiments of combined mechanical expansion and rein grouted rock bolt anchoring systems and, in particular, novel means for rotationally coupling a rock bolt and an expansion anchor threaded thereon in one direction of bolt rotation while allowing the anchor to be held rotationally stationary as the bolt is rotated in the opposite direction to effect expansion of the anchor.